If you want to check out where the San Diego locals hang out, you have to stop by Bootlegger, located on the border of Gaslamp.
The bar itself is unique, with a beautiful stone top and lined with hand-carved wooden panels imported from Mexico. There are comfortable seats no matter where you look. Although the decor is going for that dive bar feel, it's got a touch of hidden elegance. When you come in, as long as it's not too crowded, the service is highly personable.
The Bootlegger is designed somewhat to look like a 1920s speakeasy, and has some interesting art on the walls. The drinks are poured using top-grade liquors; my favorite so far (pictured) is the 'Old Fashioned'—Bulleit Bourbon, Angostura bitters, sugar, fresh lemon and orange peel. They have a good number of beers on tap and a great selection from the local micro-breweries.
I recommend the happy hour—it's not too crowded and select drinks and all appetizers are half price. For a neighborhood bar, the food is really good. The Bootlegger bar is a great place to experience the San Diego vibe.
Another cool thing is that they don't allow smoking out on the patio around the bar, so if you want to enjoy a smoke-free night, this is the place to be.
Tip: It gets impossibly crowded during any game going on at Petco Park, which is the local baseball stadium. During the late week to weekend it also gets crowded. If you want to come and chill before a night on the town, come by for the happy hour, from 3–8 p.m.